For this case we must solve the expression given for the variable "m":

We add 5 to both sides of the inequality:

Multiplying by 2 to both of the inequality:

So, finally we have:

The solution is given by all values of m less than 4.
Answer:

At start: PE only
At end: KE and energy lost to friction
PE = KE + E
E = PE - KE
= mgh - (1/2)mv^2
= (40)(9.8)(12) - (.5)(40)(10)^2
= 2704J
He burns off 750 calories every 3 hours. 250 multiplied my 3 is 750. 3 being the hours and 250 being the calories burned every hour